1. Field of the Invention
The present invention relates to improvements in a broaching machine for broaching an outer surface of a rotor of a rotor assembly which consists of the rotor and a support shaft for supporting the rotor rotatably about its axis.
2. Description of the Art
A fluid machine of a Roots type using a plurality of rotor assemblies is known. Each of the rotor assemblies consists of a rotor, and a support shaft for rotatably supporting the rotor about its axis of rotation. Opposite end portions of the support shaft project from opposite end faces of the rotor in opposite directions parallel to the axis of rotation of the rotor. For finishing the outer surface of the rotor to a desired shape with a comparatively high level of dimensional accuracy, it is known to use a broaching machine wherein a broaching cut is made by a broach which is adapted to be fed in the direction parallel to the axis of rotation of the rotor.
To finish the outer surface of the rotor on such a broaching machine, the rotor assembly must be mounted in place on the machine with a large clamping force sufficient to withstand a cutting force of a broach cutter against the rotor assembly. Further, the rotor assembly must be accurately centered with its axis of rotation aligned with the line of feed of the broach cutter, and also be precisely positioned in its circumferential direction. Consequently, the mounting and removal of the rotor assembly on and from the broaching machine are considerably cumbersome and time-consuming. Thus, the finishing of the rotor surface by the broaching machine requires a relatively long non-productive time period for mounting the workpiece and dismounting the finished workpiece, whereby the broaching machine suffers from relatively low productivity or operating efficiency.